The model boundary conditions of space weather and the space weather forecast itself are entirely dependent upon solar observations and, especially, on the knowledge about the origin of the solar wind. Coronal holes have been firmly established as the main source of the high-speed streams of the fast solar wind ( 800 km/s, Krieger et al., 1973). In contrast the source of the dense, highly-structured and sporadic slow solar wind has not yet been identified (~ 400 km/s, Cranmer, 2009.) The basic physical processes which could explain the magnetically driven plasma outflows of the fast/slow solar wind also remain a fundamental mystery.
Subramanian et al. (2010) and follow-up papers by Madjarska et al. (2012) and Huang et al. (2012), all based on Hinode data, demonstrated that small-scale jet-like events are concentrated in coronal holes and their boundaries (polar or mid-latitude) having their origin in coronal bright points. We suggested that these sporadic high-density plasma outflows are possibly one of the sources of the slow solar wind. Neugebauer (2012) proposed “that the interplanetary manifestations of X-ray jets observed in polar coronal holes during periods of low solar activity are the peaks of the so-called microstreams observed in the fast polar solar wind.” Kilpua et al. (2009) surveyed the structure of the slow solar wind during the solar minimum 2007 – 2008 with the Wind and STEREO spacecraft. Small-scale transients were frequently found in the slow solar wind and were traced to the vicinity of the coronal sector boundary.
Coronagraph observations have also revealed the sporadic occurrence of long linear structures propagating outward from the Sun’s polar regions (at solar minimum) and over a large range of latitudes (at solar maximum) (Wang et al. 1998, Wood et al. 1999, Wang & Sheely 2002). Traced back in the low solar corona, these jets were found to occur daily originating from coronal bright points.
The proposed study is a natural extension of our work on coronal hole transients mentioned above. We aim at tracking small-scale transients from coronal holes and active regions in the low and extended solar corona using multi-instrument observations. In-situ solar wind observations will also be analysed for a signature of these transients. We have obtained (MM & KG) a SWAP/Proba 2 guest investigator grant to visit the Royal Observatory of Belgium in March 2013 to observe with the SWAP imager in off-point mode. As part of this program we would like to request EIS/XRT/SOT/Hinode observations in the time period from March 13 to March 22 during 4 days. |
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